While more than 80% of patients will respond to initial radiotherapy or combination chemoradiotherapy, some patients will experience early relapse after initial therapy or be refractory to first-line therapy. These patients may be treated with second-line therapy, which may include autologous bone marrow transplantation (BMT). Patients with HL who relapse after first- and second-line therapy, or who are refractory to therapy, with or without autologous BMT, have a poor prognosis. The long-term event-free survival rate in this patient group is less than 10%; median survival is 16 months. At present, these patients have no treatment options other than investigational therapies.